There is a continuing need to lighten and strength motor vehicles and aircraft to improve fuel economy. As a result, structural members and other parts are being constructed from lighter materials. In the case of valve-train parts, weight reduction also helps to overcome inertia to achieve rapid movement of parts during engine operation.
The operation of an internal combustion engine requires that an explosive mixture of gasoline and air be delivered to a combustion zone of a cylinder during an interval timed to the intake stroke. After combustion, the products of the combustion are removed during an exhaust stroke. Intake and exhaust are accomplished by the operation of poppet valves with at least one intake valve and one exhaust valve. The opening and closing of intake and exhaust ports are affects by the rate at which the valve components operate. The timing is controlled by a camshaft driven from the engine's crankshaft.
In traditional engines, the oscillation defined by the cam profile is transferred through a valve-lifer, pushrod, and rocker arm to the valve. The masses of the components of the valve-train govern the precision of the valve timing by defining, through inertial loading factors, the accelerations attainable. Valve-trains of a minimum mass are, therefore, very desirable. Certain engine designs have minimized mass by reducing the number of valve-train components through the use of single and double overhead cams. While the overhead cam designs are effective they tend to be mechanically more complex.
Composite materials are used to achieve strength and weight reduction features not present in a single material. Composite rods are produced in limited quantities, in a labor-intensive, partially manual process, one at a time, for high performance race cars. The process used is a prepreg process where a reinforcing fiber mat coated with a resin is wrapped around a mandrel and cured to form a rod. Exterior endcaps are then secured to the exterior of the rod at each end. This process is slow, inefficient, costly and unsuitable for mass production.
Therefore, what is needed is a valve-train pushrod which is light weight, stable at high temperatures, strong, resistant to buckling, stiff, suitable for use in engines at high temperatures, and a method of manufacture which is suitable for mass production.